The disclosed embodiments of the present invention relate to calibrating a stereo camera device, and more particularly, to on-line stereo camera calibration device and method for generating stereo camera parameters.
With the development of science and technology, users are pursing stereoscopic and more real images rather than high quality images. There are two techniques of present stereo image display. One is to use a video output apparatus which collaborates with glasses (such as anaglyph glasses, polarization glasses or shutter glasses), while the other is to directly use a video output apparatus without any accompanying glasses. No matter which technique is utilized, the main theory of stereo image display is to make the left eye and the right eye see different images (i.e., one left-view image and one right-view image), thus the brain will regard the different images seen from two eyes as one stereo image.
A stereo image pair of one left-view image and one right-view image may be obtained by using a stereo camera device. The stereo camera device is a camera that has two image sensors used to take two pictures at the same time. The stereo image pair, including one left-view image and one right-view image, therefore creates the three-dimensional (3D) effect when viewed by the user. For example, a smartphone may be equipped with a stereo camera module composed of two image sensors, each having a lens. The capture result of the stereo camera module may be processed and then displayed on a 3D panel of the smartphone.
However, when a module house manufactures the stereo camera module, there maybe inevitable errors in the lens module, the image sensor module, and/or the stereo camera layout of the stereo camera module. As a result, the principle points (i.e., centers) of a left-view image and a right-view image included in one stereo image pair do not possess the X-axis colinearity, Y-axis of the left-view image is not parallel with Y-axis of the right-view image, and/or Z-axis of the left-view image is not parallel with Z-axis of the right-view image.
After the stereo camera module is assembled in the smartphone, an image processing chip of the smartphone is required to apply image calibration upon each stereo image pair generated from the stereo camera module to avoid/mitigate image quality degradation resulting from inherent errors of the stereo camera module. Based on the calibration model employed by the image processing chip of the smartphone, the module house has to perform an off-line stereo camera calibration to generate stereo camera parameters needed by the currently employed calibration model. However, when the image processing chip of the smartphone is modified to employ a different calibration model, the module house needs to perform another off-line stereo camera calibration to generate new stereo camera parameters needed by the currently employed calibration model.
Moreover, the stereo camera calibration procedure is supposed to be performed after the assembly process. Actually, the stereo camera calibration procedure is performed by the module house rather than the assembly plant. Thus, the relative relation between image sensors should keep the same in the module house and the assembly plant. However, it changes in the assembly plant. As a result, the image calibration performed based on the stereo camera parameters provided by the module house may fail to effectively mitigate image quality degradation resulting from inherent errors of the stereo camera module.